Double check

A double check means that two pieces attack the king simultaneously after one move. The usual pattern occurs when a piece moves with check and, by moving away, also opens a discovered check from a rook, bishop, or queen.

Its consequence matters more than its shape: the checked player can respond only with a king move. Capturing one checking piece or blocking one line is insufficient because the second piece would still attack the king.

The king may move to a safe square or capture one of the checking pieces itself, provided the destination is not attacked. Interposition, which places another piece on an attacking line to block it, can never solve a double check on its own.

Double check does not merely mean that a move creates two threats elsewhere on the board. Both pieces must be attacking the king in the resulting position.